A generic method and a generic arrangement are known from WO 02/082400.
Every year, speeding costs not only many human lives but also much money for medical care of the injured. Further, it causes immense property damage and also impedes the free flow of traffic. Therefore, a suitable and efficient monitoring of speed is especially important.
Radar equipment making use of the Doppler effect, for example, is used to determine and monitor the driving speed of vehicles. When the permissible speed limit is broken, one or more pictures of the vehicle are taken for purposes of documentation. Despite the efficiency of this method, monitoring is only carried out selectively at fixed or mobile points so that drivers who are aware of these monitoring points temporarily reduce their driving speed and then resume driving in excess of the permissible maximum speed.
In order to thwart this evasive behavior, a video-based measuring system was installed in the Kaisermühlen tunnel on A22 in Vienna which determines the average speed along a specified section of road and imposes a penalty when the permissible maximum speed is exceeded.
Further, International Patent Application WO 02/082400 A2 discloses an arrangement and a method for determining and storing an event in which the average speed is determined over one or more sections of road. To this end, at least two detection units are installed on the road at a distance of 500 meters or more from one another in order to determine the average speed in the section of road between the detection units and compare it with a permissible maximum speed.
When the first detection unit is passed, a first image of a vehicle is recorded, the time of the image recording is stored, and the registration number of the vehicle is determined by means of OCR (Optical Character Recognition).
When passing the next detection unit, where the vehicle is expected, a second image of the vehicle is recorded, the time of the image recording is stored, and the registration number of the vehicle is determined by OCR.
If a match is determined when comparing the vehicle registration numbers and a speeding violation is determined when the detected average speed is compared with the permitted maximum speed, a signal is sent to an output port which triggers a display device to alert the driver that he is driving at an excessive speed.
There is no suggestion in WO 02/082400 that the arrangement and the method are suitable for or intended for a conclusive capturing of a speed violation which is associated with an image recording in which the driver is discernible. Since vehicle registration number plate recognition is merely a matter of identifying alphanumeric symbols having a standardized typeface, low-resolution cameras can be used for this purpose so that these cameras are not only comparatively cheaper, but computing and storage resources are also advantageously minimized in an optimal manner.
The quantity of pixels required by a camera for vehicle registration plate recognition depends particularly upon the scene width of the image recording. When the camera is used for only one traffic lane, given an average traffic lane width of 3.6 m, then a 1.4-megapixel camera offers the minimum resolution needed for capturing a stroke thickness of a symbol of one centimeter with a good recognition rate.
Infrared-sensitive cameras are particularly well-suited for vehicle registration plate recognition because, in the infrared range, illumination can be carried out in the invisible region and the vehicle registration number plate has a particularly good reflectivity in both daytime and nighttime operation. Accordingly, sufficient contrast and brightness can be achieved in the image recordings with a corresponding illumination.
However, the intensity of the illumination is not sufficient for illuminating the passenger space.
Irrespective of the insufficient illumination of the passenger space in image recordings for capturing vehicle registration plates, the resolution is also insufficient to positively identify the driver's face.
If a high-resolution camera were used for capturing the vehicle registration plate so as also to enable the face of the driver to be discerned in this image recording and if a flash with sufficient intensity to illuminate the passenger space well enough to discern the face of the driver were generated at the same time, the reception area of the image recording device struck by the radiation reflected by the vehicle registration plate would be completely overloaded and vehicle registration plate recognition would no longer be possible.
Further, every triggering of an image recording of passing vehicles would be perceived by the driver, which is undesirable in cases where there is no traffic violation.
In countries such as Germany, where the costs-by-cause principle applies, image recordings for purposes of vehicle registration plate recognition for conclusive documentation of a speed violation are not sufficient by themselves to prosecute a speed violation.